Methods and apparatus to identify signals using a low power watermark

ABSTRACT

Methods, apparatus, systems and articles of manufacture are disclosed for signal identification using a low power watermark. Example apparatus for media identification based on watermarks includes a first processor to determine, in response to receiving a signal, if a first watermark is present in the signal using a first processing technique. The example first processor is further to provoke, in response to the first watermark being present in the signal, a second processing technique on a signal processor. The signal processor is to extract a second watermark in the signal using the second processing technique.

FIELD OF THE DISCLOSURE

This disclosure relates generally to watermarking, and, moreparticularly, to identifying signals using a low power watermark.

BACKGROUND

In recent years, use of metering devices to monitor media consumptionhas become more prevalent. Some metering devices are portable, enablingmonitoring of media consumption as a participant moves among varioussettings and media exposures. Such metering devices may be attached tothe belt or carried via other methods on the participant's body. As aresult, demand has increased for metering devices with a smaller sizeand more efficient power usage to reduce, for example, chargingfrequency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an example system constructed inaccordance with the teachings of this disclosure for signalidentification using a low power watermark.

FIG. 2 is a schematic illustration of the example household of FIG. 1depicted in accordance with the teachings of this disclosure for mediaprocessing and identification in the household using a low powerwatermark.

FIG. 3 is a block diagram showing an example implementation of theexample encoder of FIG. 1.

FIG. 4 is a block diagram showing an example implementation of theexample media monitor of FIG. 1.

FIG. 5 is a block diagram showing an example implementation of theexample watermark detector of FIG. 4 utilizing a least means squaresfilter algorithm.

FIG. 6 is a schematic of an example implementation of a mediaidentification watermark and a low power watermark.

FIG. 7 is a flowchart representative of example machine readableinstructions that may be executed to implement the example encoder toperform encoding of media identification and low power watermarks into amedia signal.

FIG. 8 is a flow chart representative of example machine readableinstructions that may be executed to implement the example media monitorto perform signal identification using a low power watermark.

FIG. 9 is a flow chart representative of example machine readableinstructions that may be executed to implement the example watermarkdetector to determine if a low power watermark is present in an audiosignal using a least means square algorithm.

FIG. 10 is a schematic representation of an example implementation ofthe lower power watermark and the media identification watermark usedfor signal identification.

FIG. 11 is a schematic illustration of an example processor platformthat may execute the instructions of FIG. 7 to implement the exampleencoder of FIGS. 1 and 3.

FIG. 12 is a schematic illustration of an example processor platformthat may execute the instructions of FIGS. 8 and 9 to implement theexample media monitor of FIGS. 1, 2 and 4.

The figures are not to scale. Wherever possible, the same referencenumbers will be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts.

DETAILED DESCRIPTION

Audio watermarking is a technique used to identify media such astelevision broadcasts, radio broadcasts, advertisements (televisionand/or radio), downloaded media, streaming media, prepackaged media,etc. Existing audio watermarking techniques identify media by embeddingone or more audio codes (e.g., one or more watermarks, etc.), such asmedia identifying information and/or an identifier that may be mapped tomedia identifying information, into an audio and/or video signal. Insome examples, characteristics of the watermark are selected to hide thewatermark (e.g., make the watermark inaudible, not visible, etc.). Asused herein, the terms “code” or “watermark” are used interchangeablyand are defined to refer to signal components that are inserted/embeddedin the audio or video of media signals (e.g., a program oradvertisement). In some examples, watermarks may be inserted for thepurpose of identifying the media or for another purpose such as tuning(e.g., a packet identifying header). As used herein “media” refers toaudio and/or visual (still or moving) content. In some implementations,to identify watermarked media, the watermark(s) are extracted and usedto access a table of reference watermarks that are mapped to mediaidentifying information.

Traditionally, media including watermarks is identified by a continuousprocess operating to identify the watermark. For example, a media signalcorresponding to media playback is monitored by an audio recordingdevice (e.g., on a media monitoring meter) and processed by a processorthat finds and extracts watermarks and identifies the watermarked mediabased on the watermarks. Since watermarks typically correspond to theparticular media with which they are associated, each watermark isunique and requires substantial processing to detect and identify withinthe recorded signal.

The device which processes watermarks may be, for example, a mediamonitor device (e.g., a meter). While some media monitors are configuredto monitor a specific location (e.g., an entertainment room in ahousehold), other media monitors are portable and carried around by aparticipant (e.g., a panelist). According to current trends and userexpectations, portable media monitors should be small enough to becomfortably (preferably non-noticeably) carried on a person's body, andhave a battery capacity such that frequent charging is not required.Current portable media monitors are approximately the size of a pagerand are typically clipped to a user's hip, which may be uncomfortableand aesthetically displeasing to the participant. In order to reduce thesize and enable a more comfortable and less noticeable portable mediamonitor, the battery size can be reduced. However, the decrease inbattery capacity disadvantageously increases the frequency with whichcharging is required.

Conventionally, decreasing the form factor of portable media monitorsand increasing the useful battery life has been difficult to achieve dueto the significant processing power utilized by the traditionalwatermark detection techniques.

In example methods, systems, and articles of manufacture disclosedherein, a first watermarked (referred to herein as a low powerwatermark) is inserted/embedded in media signals to signal that a secondwatermark is simultaneously and/or subsequently encoded. The low powerwatermark is added to the media based on encoder rules, as well ascharacteristics of a media identification watermark in order to avoidinterference between the low power watermark and the mediaidentification watermark. The low power watermark may be consistentbetween numerous media signals to enable a low power processingtechnique to detect the low power watermark without the significantprocessing needed for a conventional watermark process. For example, thelow power watermark may be a universal watermark that is generated usingthe same parameters for multiple signals pertaining to different mediapresentations. In some examples disclosed herein, the low powerwatermark is a sequence of bits encoded by modifying frequencies thatare unique compared to frequencies of the media identification watermarkand the audible output of the audio signal, to minimize audibility ofthe watermark. In some example low power watermarks, the low powerwatermark has a length equal to the media identification watermark andis included at least at the beginning of each identifiable media signal.

In some examples disclosed herein, a low power watermark encoded inmedia is detected by a low power processor including a low powerwatermark detector. In such examples, in response to the low powerwatermark being detected, the low power processor provokes a secondprocessing technique on a signal processor (e.g., separate from the lowpower processor) that is responsible for finding and extracting uniquemedia identification watermarks. In some examples, the signal processormay be in a standby mode, low power mode, etc. until the secondprocessing technique is provoked. The second processing technique, uponbeing provoked, extracts the unique media identification watermark(s),for subsequent comparison to reference watermarks to determine mediaincluded in a signal. The second processing technique continuesprocessing until media identification watermarks are no longer found, inwhich case the signal processor, in some examples, returns to a lowpower state. In some examples disclosed herein, the low power processorutilizes a low power processing technique such as a least means squareadaptive algorithm that identifies the presence of the low powerwatermark using an adaptive linear filter and a comparison between areference low power watermark and the output of the linear filter.

In contrast with conventional approaches to addressing mediaidentification, example media monitors that identify media using both alow-power watermark and a traditional media identification watermark aremore efficient and consequently enable utilization of a smaller batteryand/or a smaller media monitor. Some techniques disclosed herein reducepower consumption by reducing the amount of time media watermarkidentification processing (e.g., as opposed to low power watermarkprocessing), which is power intensive processing, is performed.

While the techniques disclosed herein are, in some examples, describedin the context of portable media monitors, the techniques may be appliedin a variety of applications, settings, or example implementations.Specifically, the techniques may be implemented in any watermarkidentification processing device and/or application to, for example,reduce power consumption.

FIG. 1 is a schematic illustration of an example system 100 constructedin accordance with the teachings of this disclosure for signalidentification using a low power watermark. The example system 100includes an example encoder 102, an example watermarked media data store104, an example transmitter 106, an example communications network 108,and an example household 110. The example household 110 includes anexample media device 112 that transmits an example watermarked audiosignal 114 to an example media monitor 116.

The example encoder 102 of the illustrated example of FIG. 1 generateswatermarks and incorporates watermarks into a media signal. The encoder102 is configured by, operated by, and/or located at a service provider,a media provider, or any other entity. The example encoder 102 receivesmedia and media identification information and outputs the media signalincluding the watermark(s). The example encoder 102 generates a mediaidentification watermark based on the received media identificationinformation. The media identification watermark is a uniqueidentification watermark that is generated with amplitude, frequency,and phase characteristics such that it is practically inaudible when themedia signal is output. Example systems for identifying media based oncodes and/or signatures are long known and were first disclosed inThomas, U.S. Pat. No. 5,481,294, which is hereby incorporated byreference in its entirety.

The example encoder 102 additionally generates a low power watermark. Insome examples, the low power watermark is a watermark applied to mediareceived by the encoder to enable a decoder to easily identify the lowpower watermark. The example low power watermark is a universalwatermark that has similar characteristics regardless of the mediasignal it is embedded in. Alternatively, the low power watermark may beany other type of watermark that is added to a media signal to signalthe insertion of an identification watermark. The example low powerwatermark may have different amplitude, wavelength, and/or phase thanthe media identification watermark in order to make the low powerwatermark distinct and easily differentiable. In some examples, theexample low power watermark is additionally generated by the exampleencoder 102 with characteristics such as to make the low power watermarksubstantially inaudible.

The example encoder 102 outputs the media with the low power watermarkand the media identification watermark included in the media signal. Insome examples, the example encoder 102 may, in response to anunidentifiable media signal being input to the encoder, not generate anywatermarks for the media signal. In such examples, the example encoder102 may be configured to look for specific characteristics (e.g.,specific audio frequencies wherein a media identification watermark maybe embedded, etc.) in the media to determine if the media identificationwatermark should be generated. In some examples, the example encoder 102generates a low power watermark when the media identification watermarkis generated, and does not generate the watermark when the mediaidentification watermark is not generated. In some examples, the exampleencoder 102 may be implemented, at least partially, as software.

The example watermarked media data store 104 of the illustrated exampleof FIG. 1 is a storage location for watermarked media. The examplewatermarked media data store 104 may be located at a media provider, ata service provider, a third-party storage facility, on a network, and/orat any other location. The watermarked media data store 104 may beimplemented by a volatile memory (e.g., a Synchronous Dynamic RandomAccess Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUSDynamic Random Access Memory (RDRAM), etc.) and/or a non-volatile memory(e.g., flash memory). The watermarked media data store 104 mayadditionally or alternatively be implemented by one or more double datarate (DDR) memories, such as DDR, DDR2, DDR3, mobile DDR (mDDR), etc.The watermarked media data store 104 may additionally or alternativelybe implemented by one or more mass storage devices such as hard diskdrive(s), compact disk drive(s) digital versatile disk drive(s), etc.While in the illustrated example the watermarked media data store 104 isillustrated as a single database, the watermarked media data store 104may be implemented by any number and/or type(s) of databases.Furthermore, the data stored in the watermarked media data store 104 maybe in any data format such as, for example, binary data, comma delimiteddata, tab delimited data, structured query language (SQL) structures,etc.

The example transmitter 106 of the illustrated example of FIG. 1transmits watermarked media from a service provider, a media provider,and/or any other entity, to the example communications network 108. Insome examples, the example transmitter 106 transmits the watermarkedmedia 104 at a media provider facility to a service provider facilityfor distribution to an audience. The example transmitter 106 may be anantenna based system, an internet streaming based system, a cabletransmission system, a satellite transmission system, and/or any othertype of transmission system. The example transmitter 106 accesseswatermarked media from the watermarked media data store 104 andtransmits the watermarked media via one or more example communicationsnetworks 108 for distribution to individual households (e.g., audienceviewers).

The example communications network 108 of the illustrated example ofFIG. 1 is a network that transmits watermarked media to a widespreadaudience. In some examples, the communications network 108 includes oneor more facilities that receive watermarked media signals from theexample transmitter 106 and process and transmit the watermarked mediasignals for distribution to the example household 110. In some examples,the communications network 108 may transmit watermarked media to theexample household 110 in response to a condition and/or state of theexample media device 112 in example household 110 (e.g., the mediadevice 112 being tuned to a channel, the media device 112 requestingspecific media content, etc.).

The example household 110 of the illustrated example of FIG. 1 is anaudience location at which media is presented. In some examples, thehousehold 110 includes multiple different audience members who may viewone or more media presentations at any time. The example household 110includes the example media device 112 and the example media monitor 116.While the household 110 is one example environment wherein the mediadevice 112 and the media monitor 116 can be implemented, in someexamples, the media monitor 116 is portable and is used to monitor mediapresented on a media device at a different location.

The example media device 112 of the illustrated example of FIG. 1receives media transmitted to the example household 110. The examplemedia device 112 outputs the example watermarked audio signal 114 withinthe example household 110. The example media device 112 may be a radio,television, computer, tablet, smart phone, and/or any other device thatoutputs audio and/or audiovisual media. The media device 112 may beconnected to a cable television connection (e.g., via a set top box,etc.), may be connected to the Internet (e.g., via a wireless router,modem, etc.) and/or may be connected to any other infrastructure toreceive media transmitted via the example communication network 108. Insome examples, the example household 110 includes multiple mediadevices, which receive and present the same and/or different media. Themedia device 112 may include speakers, and/or other audio outputcomponents to present the example watermarked audio signal 114.

The example watermarked media transmitted to the example household 110via the example communication network 108 is presented by the examplemedia device 112 as the example watermarked audio signal 114. Theexample watermarked audio signal 114 includes audio, and mayadditionally or alternatively include video. The example media device112 outputs the example watermarked audio signal 114 at a volume loudenough to be detected by the example media monitor 116.

The example media monitor 116 of the illustrated example of FIG. 1 is adevice that receives the example watermarked audio signal 114. In someexamples, the example media monitor 116 is a portable media monitor,carried by a participant in the example household 110. In some examples,the example media monitor 116 records the example watermarked audiosignal 114 as it is output by the example media device 112. The examplemedia monitor 116, after receiving the example watermarked audio signal114, detects the low power watermark previously encoded in thewatermarked audio signal 114 by the example encoder 102. In response todetecting the low power watermark, the example media monitor 116processes the watermarked audio signal 114 to extract the previouslyencoded media identification watermark from the watermarked audio signal114 for subsequent use in identifying the media corresponding to thepresented watermarked audio signal 114. The example media monitor 116may itself process the media identification watermark to identify themedia (e.g., by comparing the media identification watermark to areference database) and/or may transmit the media identificationwatermark to a central facility for identification of the media.

In operation, the example encoder 102 receives media and mediaidentification information and encodes a low power watermark and mediaidentification watermark into the signal conveying media. The exampleencoder then outputs the media with the low power watermark and themedia identification watermark for storage in the example watermarkedmedia data store 104. The example transmitter 106 accesses thewatermarked media and transmits the watermarked media via the examplecommunications network 108 to the example household 110. The examplemedia device 114 receives the watermarked media and outputs thewatermarked audio signal 114 which is received by the example mediamonitor 116. The example media monitor 116 then detects the presence ofthe low power watermark in the watermarked audio signal 114, triggeringa second processing technique to extract and/or identify the mediaidentification watermark.

FIG. 2 is an example implementation of the example household 110. Theexample household 110 includes example media devices 112 a, 112 b,example watermarked audio signals 114 a, 114 b, the example mediamonitor 116, an example audience member 202, and an example chargingdevice 204.

The example media devices 112 a, 112 b are example implementations ofthe example media device 112 of FIG. 1. The example media device 112 ais a radio that outputs the example watermarked audio signal 114 a inthe example household 110. The example media device 112 b is atelevision that outputs the example watermarked audio signal 114 b inthe example household 110 and additionally outputs audiovisual mediacontent. The example media devices 112 a, 112 b may output the same ordifferent watermarked audio signals, and may output the signalssimultaneously or at different times. In some examples, the examplemedia monitor 116 may have difficulty discerning between the exampleaudio watermarked signals 114 a, 114 b. In some examples, the examplemedia monitor 116 may be configured to filter out signals beingpresented that do not include watermarks in order to more effectivelyprocess any watermarked audio signals being presented.

The example watermarked audio signals 114 a, 114 b are output by theexample media devices 112 a, 112 b. In some examples, the examplehousehold 110 may include any number of media devices presenting anynumber of audio signals at any time.

The example audience member 202 is a person in the example household110. In examples where the example media monitor 116 is a portable mediamonitor, the example audience member 202 carries the example mediamonitor 116 on their person. In the illustrated example of FIG. 2, theexample audience member 202 carries the example media monitor 116 ontheir belt. In such an example, the media monitor 116 may only receivethe example watermarked audio signal 114 b from the example media device112 b, based on the orientation of the example media monitor 116.

The example charging device 204 recharges a battery for the examplemedia monitor 116 in examples where the example media monitor 116 is aportable media monitor. The example charging device 204 requires theexample media monitor 116 be kept on the charging station to charge thebattery. In some examples, the example media monitor 116 may not beoperational (e.g., capable of monitoring media, etc.) during thecharging operation. It is naturally advantageous for the example mediamonitor 116 to be operational for as long as possible with few chargingsessions, leaving charging for times when media is not being presented(e.g., at night, at times when no one is in the example household 110,etc.).

In operation, the example media devices 112 a, 112 b output watermarkedaudio signals 114 a, 114 b that are received by the example mediamonitor 116 carried by the example user 204. When the example mediamonitor 116 is low on battery power, the example media monitor 116 mustbe charged using the example charging device 204.

FIG. 3 is a block diagram of an example implementation of the exampleencoder 102 of FIG. 1. The example encoder 102 includes an exampleencoder rule manager 302, an example low power watermark manager 304, anexample media identification watermark manager 306, and an example mediasignal processor 308. The example media signal processor 308 includes anexample audio signal receiver 310, an example media identificationwatermark generator 312, an example low power watermark generator 314,and an example watermarked audio signal outputter 316.

The example encoder rule manager 302 of the illustrated example of FIG.3 is configured with rules associated with the encoding of audiowatermarks. In some examples, the example encoder rule manager 302 isconfigured with rules such as an attack start time, an amplitude decayrate, a watermark length, audio envelope attack, sustain, and decaycharacteristics, etc. The example encoder rule manager 302 may beconfigured to control parameters to enable the example low powerwatermark manager 304 and the example media identification watermarkmanager 306 to set parameters for watermarks that do not interfere withthe audio signal (e.g., do not create an audible artifact in the audiosignal) and are in agreement with parameters of a decoder. The exampleencoder rule manager 302 may receive rules from a media provider, aservice provider, and/or any other entity to ensure that watermarks areencoded in accordance with a decoding entity's preferences/requirements.For example, a media audience measurement entity may set the rules ofthe example encoder rule manager 302 based on developed standards/bestpractices to ensure that the watermarks may be reliably decoded foraccurate audience measurement.

The example low power watermark manager 304 of the illustrated exampleof FIG. 3 configures parameters associated with the generation of a lowpower watermark. In some examples, the example low power watermarkmanager receives rules from the example encoder rule manager 302 towhich the low power watermark must adhere. The example low powerwatermark manager 304 may be configured initially during a setup processof the example encoder 102. The example low power watermark manager 304may determine a watermark length, frequency values, amplitude values,phase values, audio envelope characteristics (e.g., attack, sustain,decay, etc.) and/or any other relevant audio parameters defining the lowpower watermark. The example low power watermark manager 304communicates rules and parameters specific to the low power watermark tothe example low power watermark generator 314. In some examples, theexample low power watermark manager 304 is configured identicallybetween multiple encoders such that the low power watermark hasconsistent characteristics across media. The example low power watermarkmanager 304 may be in communication with the example mediaidentification watermark manager 306 to ensure the low power watermarkhas different characteristics than the media identification watermark,and will consequently be identifiable.

The example media identification watermark manager 306 of theillustrated example of FIG. 3 configures parameters associated with thegeneration of a media identification watermark. In some examples, theexample media identification watermark manager 306 receives rules fromthe example encoder rule manager 302 to which the media identificationwatermark must adhere. The example media identification watermarkmanager 306 may be configured with general rules regarding restrictionson watermark length, amplitude decay, frequency values, phase values,audio envelope characteristics, etc. In some examples, the example mediaidentification watermark manager 306 communicates rules and parametersspecific to the media identification watermark to the example mediaidentification watermark generator 312. The example media identificationwatermark manager 306 may communicate rules that act as boundaryconditions and restrictions on watermark implementation, as opposed toexplicitly defining the media identification watermark, which will bevary based on the specific media audio signal.

The example media signal processor 308 of the illustrated example ofFIG. 3 receives audio signals, incorporate watermarks into the audiosignals, and output audio signals. The example media signal processor308 receives media audio signals as well as media identificationinformation and outputs a watermarked audio signal. The example mediasignal processor 308 includes the example audio signal receiver 310, theexample media identification watermark generator 312, the example lowpower watermark generator 314, and the example watermarked audio signaloutputter 316.

The example audio signal receiver 310 of the illustrated example of FIG.3 receives media audio signals for watermarking. In some examples, theaudio signal receiver 310 receives the audio signals via a network(e.g., the Internet) from a media content provider or other entity. Theexample audio signal receiver 310 subsequently transmits the media audiosignal to the example media identification watermark generator 312and/or the example low power watermark generator 314 for implementationof watermarks.

The example media identification watermark generator 312 of theillustrated example of FIG. 3 generates media identification watermarksbased on the rules and parameters maintained by the example mediaidentification watermark manager 306 and based on media identificationinformation. The example media identification watermark generator 306receives media identification information pertaining to the media audiosignal received by the example audio signal receiver 310. The mediaidentification information may be encoded in the watermark included inthe audio signal. In some examples, the media identification informationmay be a reference watermark previously generated for the media. In suchan example, the media identification watermark generator 312incorporates the reference watermark into the audio signal, and/orgenerates a watermark based on the reference watermark. In someexamples, the example media identification watermark generator 312analyzes the media audio signal received by the example audio signalreceiver 310, and generates, based on the parameters set by the mediaidentification watermark manger 306, a media identification watermark.In such an example, a separate encoder may generate the mediaidentification watermark based on a similar set of parameters to thoseof the example media identification watermark manager 306. In such anexample, when similar media is conveyed in the signal, a similar mediaidentification watermark is generated for the same media, thus enablingmultiple encoders to generate similar media identification watermarks.In some examples, the example media identification watermark generator312 may additionally access and/or receive metadata associated with themedia audio signal that provides additional parameters and/orcharacteristic information associated with the media audio signal toenable an optimal and/or consistent watermark placement for the mediaaudio signal. In some examples, the example media identificationwatermark generator 312 may communicate with the example low powerwatermark generator 314 to ensure the media identification watermarkdoes not have conflicting characteristics with the low power watermarkthat may cause interference and difficulty detecting and/or extractingthe watermarks. An example implementation of the media identificationwatermark, as can be generated by the example media identificationwatermark generator 312, is illustrated in FIG. 6.

The example low power watermark generator 314 of the illustrated exampleof FIG. 3 generates low power watermarks based on the rules andparameters maintained by the example low power watermark manager 304. Insome examples, the example low power watermark generator 314 is incommunication with the example media identification watermark generator312 to ensure the low power watermark does not have interferingcharacteristics relative to the example media identification watermark.In some examples, the low power watermark generator 314 generates a lowpower watermark for every instance of a media identification watermark.In some examples, the low power watermark has different frequency,amplitude, and/or phase characteristics such as to be distinct from themedia identification watermark, and to be substantially inaudible. Insome examples, the example low power watermark generator 314 generates alow power watermark at the beginning (e.g., the first instance, etc.) ofthe media identification watermark. In such examples, the example lowpower watermark generator 314 may only generate one or more low powerwatermarks to indicate the start of a media audio signal. In such anexample, the example low power watermark generator 314 may access themedia identification information accessed by the example mediaidentification watermark generator 312 to determine when a media audiosignal begins and/or ends. In some examples, the example low powerwatermark generator 314 may modify the media identification watermark tointroduce low power watermark characteristics, creating a low powerwatermark integrated into the media identification watermark. Forexample, the example low power watermark generator 314 may alter thestart bit (e.g., indicating the start of the media identificationwatermark) and the sync bit (e.g., a bit used to align and decode anincoming asynchronous media identification watermark) to havecharacteristics that are distinct and easily identifiable by a low powerprocess on a decoder. In some examples, the low power watermark hasrepeatable audio characteristics, such as alternating between twodistinct frequencies. The example low power watermark generator 314 maygenerate any low power watermark such that the watermark is distinctfrom the media identification watermark and is identifiable. The examplelow power watermark generator 314 may generate a watermark withcharacteristics similar to the example low power watermark of theillustrated example of FIG. 6.

The example watermarked audio signal outputter 316 of the illustratedexample of FIG. 3 outputs the watermarked audio signal. In someexamples, the example watermarked audio signal outputter 316 outputs thewatermarked audio signal to a data store, such as the examplewatermarked media data store 104 of the illustrated example of FIG. 1.In some examples, the example watermarked audio signal outputter 316acts as a transmitter and transmits the watermarked audio signal to acommunications network and/or to a platform for presentation to anaudience.

In operation, the example encoder rules manager 302 maintains overallparameters associated with watermarking, working in conjunction with theexample low power watermark manager 304 and the example mediaidentification watermark manager 306 to set characteristics surroundingthe generation of watermarks for media received by the encoder. Theexample media signal processor 308 processes newly received audiosignals by first receiving the media audio signal via the example audiosignal receiver 310. The example media identification watermarkgenerator 312 then receives media identification information andgenerates a media identification watermark for the media audio signal.The example low power watermark generator 314 generates a low powerwatermark for the media audio signal. Finally, the example watermarkedaudio signal outputter 316 outputs the watermarked audio signalincluding the media identification watermark and the low powerwatermark.

While an example manner of implementing the example encoder 102 of FIG.1 is illustrated in FIG. 3, one or more of the elements, processesand/or devices illustrated in FIG. 3 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.Further, the example encoder rule manager 302, the example low powerwatermark manager 304, the example media identification watermarkmanager 306, the example media signal processor 308, the example audiosignal receiver 310, the example media identification watermarkgenerator 312, the example low power watermark generator 314, theexample watermarked audio signal outputter 316 and/or, more generally,the example encoder 102 of FIG. 3 may be implemented by hardware,software, firmware and/or any combination of hardware, software and/orfirmware. Thus, for example, any of the example encoder rule manager302, the example low power watermark manager 304, the example mediaidentification watermark manager 306, the example media signal processor308, the example audio signal receiver 310, the example mediaidentification watermark generator 312, the example low power watermarkgenerator 314, the example watermarked audio signal outputter 316and/or, more generally, the example encoder 102 of FIG. 3 could beimplemented by one or more analog or digital circuit(s), logic circuits,programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)) and/or fieldprogrammable logic device(s) (FPLD(s)). When reading any of theapparatus or system claims of this patent to cover a purely softwareand/or firmware implementation, at least one of the example encoder rulemanager 302, the example low power watermark manager 304, the examplemedia identification watermark manager 306, the example media signalprocessor 308, the example audio signal receiver 310, the example mediaidentification watermark generator 312, the example low power watermarkgenerator 314, the example watermarked audio signal outputter 316and/or, more generally, the example encoder 102 of FIG. 3 is/are herebyexpressly defined to include a non-transitory computer readable storagedevice or storage disk such as a memory, a digital versatile disk (DVD),a compact disk (CD), a Blu-ray disk, etc. including the software and/orfirmware. Further still, the example encoder 102 of FIG. 1 may includeone or more elements, processes and/or devices in addition to, orinstead of, those illustrated in FIG. 3, and/or may include more thanone of any or all of the illustrated elements, processes and devices.

FIG. 4 is a block diagram showing an example implementation of theexample media monitor 116 of FIG. 1. The example media monitor 116includes an example decoder 402. The example decoder 402 includes anexample analog to digital converter 404, an example low power processor406, an example digital signal receiver 408, an example buffer manager410, an example watermark detector 412, an example digital signalprocessor initiator 414, an example buffer data store 416, an exampledigital signal processor 418, and an example data store 420.

The example decoder 402 of the illustrated example of FIG. 4 decodeswatermarks in watermarked audio signals received by the example mediamonitor 116. The example decoder 402 includes the example low powerprocessor 406 to detect a low power watermark in the watermarked audiosignal and an example digital signal processor 418 to extract a mediaidentification watermark from the watermarked audio signal. In someexamples, the example decoder 402 may be implemented, at leastpartially, as software. In some examples, the decoder 402 receives,additionally or alternatively to watermarked audio signals, audiosignals without watermarks, and/or with watermarks that are notidentifiable. The example decoder 402 includes an example low powerprocessor including an example watermark detector 412 to continuallyprocess the audio signals received by the example decoder 402 anddetermine if recognizable watermarks are present. The example decoder402 thus saves power by running the example digital signal processor 418following the determination that recognizable watermarks are present bythe example watermark detector 412.

The example analog to digital converter 404 of the illustrated exampleof FIG. 4 receives audio signals and convert the audio signals to adigital format. The example analog to digital converter 404 converts thewatermarked audio signals and/or audio signals without watermarks todigital signals in order for the signals to be more easily analyzed bythe example low power processor 406 and the example digital signalprocessor 418. In some examples, the example analog to digital converter404 transmits the digital message to the example digital signal receiver408 of the example low power processor 406, as well as to the examplebuffer data store 416. In some examples, the audio signals may bereceived by the example decoder in a digital format. In such an example,the example analog to digital converter 404 may simply transmit theaudio signals to the example digital signal receiver 408 and the examplebuffer data store 416 in their original format.

The example low power processor 406 of the illustrated example of FIG. 4detects low power watermarks and provoke the example digital signalprocessor 418 to extract media identification watermarks. The examplelow power processor 406 includes the example digital signal receiver 408for receiving audio signals, the example buffer manager 410 formaintaining the example buffer data store 416, an example watermarkdetector 412 for detecting low power watermarks, and an example digitalsignal processor initiator 414 for provoking the example digital signalprocessor 418.

The example digital signal receiver 408 of the illustrated example ofFIG. 4 receives signals processed by the example analog to digitalconverter 404. In some examples, the example digital signal receiver 408may directly receive audio signals as they are transmitted to theexample media monitor, in examples where the audio signals aretransmitted as digital signals. In some examples, the example digitalsignal receiver 408 communicates with the example buffer manager 410upon receiving an audio signal to inform the example buffer manager 410of a time corresponding with receipt of the audio signal. The exampledigital signal receiver 408 transmits the audio signal to the examplewatermark detector 412. In some examples, the audio signal may bedirectly transmitted to the example watermark detector 412 upon receiptat the example decoder 402. In some examples, instead of the audiosignals being transmitted to the example low power processor 406, thewatermarked audio signals may be stored in the example buffer data store416 and accessed by the example watermark detector 412 to determine thepresence of the low power watermark.

The example buffer manager 410 of the illustrated example of FIG. 4maintains the example buffer data store 416. In some examples, thebuffer manager 410 determines if audio signal(s) stored in the examplebuffer data store 416 are currently being processed, and deletes theaudio signal(s) if a predetermined buffer period has passed and theaudio signals are not being processed. In such examples, thepredetermined buffer period may be an amount of time corresponding tothe amount of time the example watermark detector 412 requires todetermine if a low power watermark is present in the audio signal(s). Insome examples, the example buffer manager 410 begins a timer upondetermining an audio signal has been received by the example digitalsignal receiver 408 and/or the example buffer data store 416. In suchexamples, upon the timer value associated with an audio signalsatisfying a threshold (e.g., reaching the predetermined buffer period,a size limit, etc.), in the absence of a signal from the examplewatermark detector indicating a low power watermark has been detectedand/or a signal from the example digital signal processor indicating thesignal is being processed, the audio signal is deleted. In someexamples, the example buffer manager 410 may determine if the digitalsignal processor is in a high power state (e.g., awake), indicating theaudio signals in the buffer may currently be undergoing processing. Insome examples, the example buffer manager 410 may determine whether theaudio signals are being processed by the example watermark detector 412and/or the example digital signal processor 418 based on an indicationfrom the example buffer data store 416 (e.g., an indicator that the datais currently being accessed). In such examples, the example buffermanager 410 may delete the audio signals once the data is no longerbeing processed, based on the indication from the example buffer datastore 416.

The example watermark detector 412 of the illustrated example of FIG. 4detects the presence of a low power watermark in the audio signal. Insome examples, the example watermark detector 412 is informed as to thecharacteristics of the low power watermark that are added by the encoder(e.g., added by the example low power watermark generator 314 of theexample encoder 102 of FIG. 2). The example watermark detector 412utilizes a least means squares algorithm, described in further detail inthe block diagram 500 of FIG. 5. In some examples, the example watermarkdetector 412 outputs an error value, representing a difference betweenthe known low power watermark and the watermark found by the examplewatermark detector 412 in the audio signal. In such examples, theexample digital signal processor initiator 414 may determine if theerror value satisfies a threshold (e.g., is below a certain value) toindicate that the low power watermark has been detected. In someexamples, the example watermark detector 412 itself may determine if theerror value satisfies the threshold and outputs a determination to theexample digital signal processor initiator 414 as to whether the lowpower watermark was found. In some examples, the example watermarkdetector 412 continually analyzes any signal added to the example bufferdata store 416 to determine if the low power watermark is present. Theexample watermark detector 412, upon finding the low power watermark,may communicate with the example digital signal process initiator 414 toprovoke the example digital signal processor 418 to extract mediaidentification watermarks. In some examples, the example watermarkdetector 412 may be made inactive (e.g., in a lower power state relativeto an active power state) when the example digital signal processor 418is processing a signal. In such an example, the example digital signalprocessor 418 is made inactive once a threshold amount of time, and/oramount of the audio signal under analysis, passes without finding amedia identification watermark to extract. In such an example, when theexample digital signal processor 418 is made inactive, the examplewatermark detector 412 becomes fully active again (e.g., enters a higherpower state relative to the lower power state) and continues continuallyanalyzing any signal added to the example buffer data store 416.

The example digital signal processor initiator 414 of the illustratedexample of FIG. 4 is responsible for performing operations to ensure theexample digital signal processor 418 extracts media identificationwatermarks from a watermarked audio signal in response to the examplewatermark detector 412 detecting the low power watermark in thewatermarked audio signal. The example digital signal processor initiator414 may receive a determination from the example watermark detector 412that a watermarked audio signal currently being processed includes thelow power watermark. In response to such a determination, the exampledigital signal processor initiator 414 communicates with the exampledigital signal processor 418 to provoke the example digital signalprocessor 418 to extract media identification watermarks from thewatermarked audio signal. In some examples, the example digital signalprocessor initiator 414 may provoke the example digital signal processor418 to enter an active (e.g., higher power) state to perform aprocessing technique (e.g., the watermark extraction). In some examples,the watermark detector 412 additionally or alternatively communicateswith the example buffer data store 416 to transmit the watermarked audiosignal to the example digital signal processor 418. In some examples,the example buffer data store 416 transmitting the watermarked audiosignal to the example digital signal processor 418 may be sufficient toprovoke the example digital signal processor. In some examples, theexample digital signal processor initiator 414 may communicate with theexample buffer manager 410 to ensure that the watermarked audio signals(as identified by the example watermark detector 412) in the examplebuffer data store 416 are not deleted, at least until the mediaidentification watermarks are extracted from the watermarked audiosignals.

The example buffer data store 416 of the illustrated example of FIG. 4is used to store audio signals received by the example decoder 402 untilthe audio signals are determined to not include identifiable watermarks,or until media identification watermarks are extracted from the audiosignals including identifiable watermarks. The example buffer data store416 transmits signals that have been identified to be watermarked audiosignals (e.g., by the example watermark detector 412, as indicated bythe example digital signal processor initiator 414) to the exampledigital signal processor 418. The example buffer data store 416 ismanaged by the example buffer manager 410. In some examples, the examplebuffer data store 416 may be managed by any other component of theexample media monitor 116, and/or may include logic internal to theexample buffer data store 416 for management of the audio signals storedin the example buffer data store 416. The example buffer data store 416may be implemented by a volatile memory (e.g., a Synchronous DynamicRandom Access Memory (SDRAM), Dynamic Random Access Memory (DRAM),RAMBUS Dynamic Random Access Memory (RDRAM), etc.) and/or a non-volatilememory (e.g., flash memory). The example buffer data store 416 mayadditionally or alternatively be implemented by one or more double datarate (DDR) memories, such as DDR, DDR2, DDR3, mobile DDR (mDDR), etc.The example buffer data store 416 may additionally or alternatively beimplemented by one or more mass storage devices such as hard diskdrive(s), compact disk drive(s) digital versatile disk drive(s), etc.While in the illustrated example the buffer data store 416 isillustrated as a single database, the example buffer data store 416 maybe implemented by any number and/or type(s) of databases. Furthermore,the data stored in the example buffer data store 416 may be in any dataformat such as, for example, binary data, comma delimited data, tabdelimited data, structured query language (SQL) structures, etc.

The example digital signal processor 418 of the illustrated example ofFIG. 4 extracts media identification watermarks from watermarked audiosignals. In some examples, the example digital signal processor 418 maybe configured to identify characteristics of the watermarked audiosignal corresponding to the parameters of an encoder that generated themedia identification watermarks (e.g., parameters as set by the exampleencoder rule manager 302 and the example media identification watermarkmanager 306 of the illustrated example of FIG. 3) to extract a mediaidentification watermark from the watermarked audio signals. In someexamples, the example digital signal processor 418 remains in a lowpower state (e.g., such as a sleep mode) unless the example watermarkdetector 412 detects the low power watermark, indicating the presence ofwatermarked audio signals, or unless the digital signal processor 418 iscurrently extracting media identification watermarks from a watermarkedaudio signal. In such examples, the example digital signal processor 418may be configured with a threshold amount of time (or a threshold amountof the audio signal) after which, if no further media identificationwatermarks are found and extracted when analyzing a watermarked audiosignal, the example digital signal processor 418 returns to the lowpower state. In some examples, the example digital signal processor 418may only remain in a processing state (e.g., a higher power state) ifthe low power watermark is detected, as indicated by the examplewatermark detector 412 and/or communicated by the example digital signalprocessor initiator 414. In some examples, the example digital signalprocessor 418 stores the extracted media identification watermarksand/or the watermarked audio signals in the example data store 420. Insome examples, the example digital signal processor 418 transmits theextracted media identification watermarks to a component on the examplemedia monitor 116 and/or a component located at a central facility foridentification and attribution of the media based on the mediaidentification watermarks.

The example data store 420 of the illustrated example of FIG. 4 is astorage location for the storage of data associated with the extractionof media identification watermarks. In some examples, the exampledigital signal processor 418 may store the extracted mediaidentification watermarks in the example data store 420. In someexamples, the example digital signal processor 418 may transmit thewatermarked audio signal to be stored in the example data store 420, ina case where, for example, the watermarked audio signal is stored untilthe media identification watermark is identified. In some examples, theexample data store 420 may act as an additional buffer, storing thewatermarked audio signals and/or the extracted media identificationwatermarks for a certain amount of time after the extraction of themedia identification watermarks. The example data store 420 may beimplemented by a volatile memory (e.g., a Synchronous Dynamic RandomAccess Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUSDynamic Random Access Memory (RDRAM), etc.) and/or a non-volatile memory(e.g., flash memory). The example data store 420 may additionally oralternatively be implemented by one or more double data rate (DDR)memories, such as DDR, DDR2, DDR3, mobile DDR (mDDR), etc. The exampledata store 420 may additionally or alternatively be implemented by oneor more mass storage devices such as hard disk drive(s), compact diskdrive(s) digital versatile disk drive(s), etc. While in the illustratedexample the example data store 420 is illustrated as a single database,the example data store 420 may be implemented by any number and/ortype(s) of databases. Furthermore, the data stored in the example datastore 420 may be in any data format such as, for example, binary data,comma delimited data, tab delimited data, structured query language(SQL) structures, etc.

In operation, the example media monitor 116 includes an example decoder402, including an example analog to digital converter 404 that receiveswatermarked audio signals and audio signals without watermarks. Theexample analog to digital converter 404 converts the analog audiosignals to digital audio signals that are transmitted to the example lowpower processor 406. Specifically, the digital audio signals aretransmitted to the example digital audio signal receiver 408 and to theexample buffer data store 416. The example buffer manager 410 managesthe example buffer data store to delete audio signals that have beenprocessed and/or will not be processed (e.g., due to not includingwatermarks). The example watermark detector 412 receives the audiosignal from the example digital signal receiver 408 and determines ifthe audio signal includes a low power watermark. In response to theaudio signal including the lower power watermark, the example digitalsignal processor initiator 414 communicates with the example buffer datastore 416 to have the watermarked audio signal transmitted to theexample digital signal processor 418. The example digital signalprocessor 418 then extracts media identification watermarks from thewatermarked audio signal and may store the extracted mediaidentification watermark in the example data store 420.

While an example manner of implementing the example media monitor 116 ofFIGS. 1 and 2 is illustrated in FIG. 4, one or more of the elements,processes and/or devices illustrated in FIG. 4 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.Further, the example decoder 402, the example analog to digitalconverter 404, the example low power processor 406, the example digitalsignal receiver 408, the example buffer manager 410, the examplewatermark detector 412, the example digital signal processor initiator414, the example buffer data store 416, the example digital signalprocessor 418, the example data store 420 and/or, more generally, themedia monitor 116 of FIG. 4 may be implemented by hardware, software,firmware and/or any combination of hardware, software and/or firmware.Thus, for example, any of the example decoder 402, the example analog todigital converter 404, the example low power processor 406, the exampledigital signal receiver 408, the example buffer manager 410, the examplewatermark detector 412, the example digital signal processor initiator414, the example buffer data store 416, the example digital signalprocessor 418, the example data store 420 and/or, more generally, themedia monitor 116 of FIG. 4 could be implemented by one or more analogor digital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)).When reading any of the apparatus or system claims of this patent tocover a purely software and/or firmware implementation, at least one ofthe example decoder 402, the example analog to digital converter 404,the example low power processor 406, the example digital signal receiver408, the example buffer manager 410, the example watermark detector 412,the example digital signal processor initiator 414, the example bufferdata store 416, the example digital signal processor 418, the exampledata store 420 and/or, more generally, the media monitor 116 of FIG. 4is/are hereby expressly defined to include a non-transitory computerreadable storage device or storage disk such as a memory, a digitalversatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc.including the software and/or firmware. Further still, the example mediamonitor 116 of FIGS. 1-2 may include one or more elements, processesand/or devices in addition to, or instead of, those illustrated in FIG.4, and/or may include more than one of any or all of the illustratedelements, processes and devices.

FIG. 5 is a block diagram showing an example implementation of theexample watermark detector 410 of FIG. 4 utilizing a least means squaresfilter algorithm. The example watermark detector 410 includes an exampleaudio signal 502, an example linear filter 504, an example filteredwatermark 506, an example reference low power watermark 508, an examplesumming function 510, an example error value 512, and an exampleadaptive algorithm 514.

The example linear filter 504 of the illustrated example of FIG. 5receives the example audio signal 502 and performs linear filtering toisolate the low power watermark from the example audio signal 502. Theexample linear filter 504 may be configured with multiple coefficientsthat define the filtering operation. In some examples, the coefficientsof the example linear filter 504 may be adjusted by an output of theexample adaptive algorithm 514 in an effort to reduce the error value512 associated with the filtered watermark 506 relative to the low powerwatermark 508 when the audio signal 502 includes the lower powerwatermark. The example linear filter 504 outputs the example filteredwatermark 506, representative of the filter's attempt to isolate the lowpower watermark in the example audio signal 502. In some examples, wherethe example audio signal 502 does not include the low power watermark,the example filtered watermark 506 may be different than the low powerwatermark.

The example summing function 510 of the illustrated example of FIG. 5receives the example filtered watermark 506 and the example referencelow power watermark 508 and determines the difference between the twosignals. The example summing function 510 may, for example, subtract theexample filtered watermark from the example reference low powerwatermark 508, or perform the reverse operation. In some examples, theexample summing function 510 may be any means of comparing two signalsto determine a difference between them and output a value representativeof the comparison. In some examples, the example summing function 510outputs an error value representative of the difference between theexample reference low power watermark 508 and the example filteredwatermark 506. In some examples, the example summing function 510outputs a determination corresponding to whether the example audiosignal 502 includes the low power watermark. In such examples, thedetermination may be based on whether the difference between the examplereference low power watermark 508 and the example filtered watermark 506(e.g., an error value) satisfies a threshold. The example summingfunction 510 may additionally or alternatively perform any otheroperations to determine, based on the example filtered watermark 506 andthe example reference low power watermark 508, whether the example audiosignal 502 includes the low power watermark.

The example adaptive algorithm 514 of the illustrated example of FIG. 5receives the example audio signal 512 and the example error value 512and performs operations to adjust the coefficients of the example linearfilter 504. The adaptive algorithm 514 adjusts the coefficients suchthat when an audio signal including the low power watermark is input tothe example linear filter 504, the resulting filtered watermark 506 issimilar enough to the example reference low power watermark 508 toenable detection of the low power watermark. In some examples, theexample adaptive algorithm 512 adjusts the coefficients of the examplelinear filter 504 to reduce the error value received by adjusting thecoefficients in a direction opposite and of corresponding amplitude tothe error value at a specific frequency. For example, the exampleadaptive algorithm 514, upon seeing a large error value (e.g.,difference) between the example filtered watermark 506 and the examplereference low power watermark 508 at a specific frequency, may adjust acoefficient corresponding to the frequency in the example linear filter504 to attempt to reduce this error. In some examples, the adaptivealgorithm 514 may adjust the example linear filter 504 and/or theexample summing function 510 using any operation to make the examplelinear filter 504 more effective at isolating the low power watermark inthe example audio signal 502.

In operation, the example audio signal 502 is input to the examplelinear filter 504 to generate the example filtered watermark 506. Theexample filtered watermark 506 is then input, along with the examplereference low power watermark 508 to the example summing function 510 todetermine the example error value 512. The example error value 512 isthen input to the example adaptive algorithm 512 to update coefficientsof the example linear filter 504 for improved low power watermarkrecognition.

While an example manner of implementing the watermark detector 410 isillustrated in FIG. 5, one or more of the elements, processes and/ordevices illustrated in FIG. 5 may be combined, divided, re-arranged,omitted, eliminated and/or implemented in any other way. Further, theexample audio signal 502, the example linear filter 504, the examplefiltered watermark 506, the example reference low power watermark 508,the example summing function 510, the example error value 512, theexample adaptive algorithm 514 and/or, more generally, the examplewatermark detector 410 of FIG. 5 may be implemented by hardware,software, firmware and/or any combination of hardware, software and/orfirmware. Thus, for example, any of the example audio signal 502, theexample linear filter 504, the example filtered watermark 506, theexample reference low power watermark 508, the example summing function510, the example error value 512, the example adaptive algorithm 514and/or, more generally, the example watermark detector 410 of FIG. 5could be implemented by one or more analog or digital circuit(s), logiccircuits, programmable processor(s), application specific integratedcircuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or fieldprogrammable logic device(s) (FPLD(s)). When reading any of theapparatus or system claims of this patent to cover a purely softwareand/or firmware implementation, at least one of the example audio signal502, the example linear filter 504, the example filtered watermark 506,the example reference low power watermark 508, the example summingfunction 510, the example error value 512, the example adaptivealgorithm 514 and/or, more generally, the example watermark detector 410of FIG. 5 is/are hereby expressly defined to include a non-transitorycomputer readable storage device or storage disk such as a memory, adigital versatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc.including the software and/or firmware. Further still, the examplewatermark detector 410 of FIG. 3 may include one or more elements,processes and/or devices in addition to, or instead of, thoseillustrated in FIG. 5, and/or may include more than one of any or all ofthe illustrated elements, processes and devices.

FIG. 6 is a schematic 600 of an example implementation of a mediaidentification watermark and a low power watermark. The schematic 600includes an example media identification watermark 602 including anexample watermark length 604, an example start bit 606, an examplestation identification section 608, an example sync section 610, anexample offset section 612, and an example timestamp section 614. Theschematic 600 additionally includes an example low power watermark 616including an example first bit 618 and an example second bit 620. Theexample media identification watermark 602 and the example low powerwatermark 616 are, in some examples, generated in accordance with theexample instructions 700 by the example encoder 102 of FIGS. 1 and 3.

The example media identification watermark 602 of the illustratedexample of FIG. 6 is a unique watermark specific to a media audiosignal. The example media identification watermark 602 has an examplewatermark length 604 corresponding to the amount of information (e.g.,the number of bits), and/or an amount of time between the start of themedia identification watermark 602 and the end of the mediaidentification watermark 602. In some examples, multiple mediaidentification watermarks may be incorporated back-to-back into themedia audio signal. The example watermark length 604 corresponds to theminimum length of the audio signal that includes the entire examplemedia identification watermark 602. The example media identificationwatermark 602 additionally includes an example start bit 606. Theexample start bit 606 indicates the beginning of the watermark. Inexamples wherein there are multiple media signals being playedconsecutively, the example start bit 606 indicates the beginning of anew media signal, and/or a new watermark instance. Following the examplestart bit 606, the example media identification watermark 602 includes astation identification section 608. The example station identificationsection 608 includes bits that are encoded to specifically pertain to anidentifying characteristic (e.g., a service provider, a media provider,a broadcaster, etc.) for the media. In some examples, the examplestation identification section 608 is useful for audience attribution,as it enables identification of the station that broadcast the examplemedia identification watermark 602. The example media identificationwatermark 602 additionally includes an example sync bit 610 to align anddecode an incoming asynchronous media identification watermark. Theexample media identification watermark 602 includes an example offsetsection 612 following the example sync bit 610. The example offsetsection 612 is a section that correlates with (e.g. may be equal to, mayhaving a mathematical predictable relationship with, etc.) the firstsection (e.g., the station identification section 608, etc.) of themedia identification watermark 602, providing validation of the mediaidentification information included in the watermark. Following theexample offset section 612, the example media identification watermark602 includes an example timestamp section 614. The example timestampsection 614 includes bits corresponding to a time at which the examplewatermark is decoded. In the illustrated example of FIG. 6, the examplemedia identification watermark 602 includes assigned letterscorresponding to each bit (e.g., A, B, C, etc.). The example letters maycorrespond to a unique characteristic of the audio signal for the bit.For example, the letters may correspond to frequencies, phase values,and/or amplitude values at which the bit is encoded into the audiosignal. The example bits are distinct from the audible, perceptiblecontent of the audio signal and may have unique audio characteristicsreflective of this.

The example low power watermark 616 of the illustrated example of FIG. 6is a watermark with distinct characteristics from the example mediaidentification watermark 602. The example low power watermark 616includes an example first bit 618 (e.g., a first section/portion, afirst watermark that is a part of the overall low power watermark 616,etc.) and an example second bit 620 (e.g., a second section/portion, asecond watermark that is a part of the overall low power watermark 616,etc.). The example first bit 618 has an assigned letter of “Y,”corresponding to the bit. As in the example media identificationwatermark 602, the assigned letter represents a unique characteristic ofthe audio signal corresponding to the letter. For example, bitsincluding the assigned letter “Y” may have the same frequency,amplitude, and/or phase characteristics, the one or more characteristicsbeing unique to bits with this assigned letter. In some examples, the“X” bit, section, and/or watermark includes a number of unique frequencytones. Similarly, the example second bit 620 has an assigned letter of“Z,” corresponding to a unique characteristic of the bits assigned thisletter. In some examples, the “Z” bit, section, and/or watermarkincludes a number of unique frequency tones, one or more of which aredifferent than one or more of the frequency tones included in the “X”bit, section, and/or watermark. In some examples, the uniquecharacteristics of the respective bits may make the low power watermark616 distinct from the content of the audio signal, to ensure the lowpower watermark does not interfere with the audible content of the audiosignal. In some examples, the example low power watermark 616 includesbits with the same characteristics as the example first bit 618 and theexample second bit 620 in alternating order throughout the watermarklength 604. The example low power watermark 616 is therefore highlypredictable and easily identifiable, assuming the unique audiocharacteristics corresponding to the first bit 618 (e.g., thecharacteristic “Y”) and the second bit 620 (e.g., the characteristic“Z”) are selected to be distinct from the rest of the audio signal. Insome examples, the low power watermark may have any pattern and/orconfiguration of audio characteristics to enable an easily identifiablewatermark. In the illustrated example of FIG. 6, the low power watermark616 has the same example watermark length 604 as the example mediaidentification watermark 602. In some examples, the example low powerwatermark 616 may have any length. The example low power watermark 616may additionally have any audio characteristics that enable a low powerprocessor to detect the low power watermark. Unlike the example mediaidentification watermark 602, the example low power watermark 616 hascharacteristics that may remain constant over numerous different audiosignals to enable fast and low power detection of the example low powerwatermark 616.

A flowchart representative of example machine readable instructions forimplementing the example encoder 102 of FIG. 3 is shown in FIG. 7. Inthis example, the machine readable instructions comprise a program forexecution by a processor such as a processor 1112 shown in the exampleprocessor platform 1100 discussed below in connection with FIG. 11. Theprogram may be embodied in software stored on a non-transitory computerreadable storage medium such as a CD-ROM, a floppy disk, a hard drive, aDVD, a Blu-ray disk, or a memory associated with the processor 1112, butthe entire program and/or parts thereof could alternatively be executedby a device other than the processor 1112 and/or embodied in firmware ordedicated hardware. Further, although the example program is describedwith reference to the flowchart illustrated in FIG. 7, many othermethods of implementing the example encoder 102 may alternatively beused. For example, the order of execution of the blocks may be changed,and/or some of the blocks described may be changed, eliminated, orcombined. Additionally or alternatively, any or all of the blocks may beimplemented by one or more hardware circuits (e.g., discrete and/orintegrated analog and/or digital circuitry, a Field Programmable GateArray (FPGA), an Application Specific Integrated circuit (ASIC), acomparator, an operational-amplifier (op-amp), a logic circuit, etc.)structured to perform the corresponding operation without executingsoftware or firmware.

As mentioned above, the example processes of FIG. 7 may be implementedusing coded instructions (e.g., computer and/or machine readableinstructions) stored on a non-transitory computer and/or machinereadable medium such as a hard disk drive, a flash memory, a read-onlymemory, a CD, a DVD, a cache, a random-access memory and/or any otherstorage device or storage disk in which information is stored for anyduration (e.g., for extended time periods, permanently, for briefinstances, for temporarily buffering, and/or for caching of theinformation). As used herein, the term non-transitory computer readablemedium is expressly defined to include any type of computer readablestorage device and/or storage disk and to exclude propagating signalsand to exclude transmission media. “Including” and “comprising” (and allforms and tenses thereof) are used herein to be open ended terms. Thus,whenever a claim lists anything following any form of “include” or“comprise” (e.g., comprises, includes, comprising, including, etc.), itis to be understood that additional elements, terms, etc. may be presentwithout falling outside the scope of the corresponding claim. As usedherein, when the phrase “at least” is used as the transition term in apreamble of a claim, it is open ended in the same manner as the term“comprising” and “including” are open ended.

Example machine readable instructions 700 that may be executed toperform encoding of media identification and low power watermarks into amedia signal are illustrated in FIG. 7. With reference to the precedingfigures and associated descriptions, the example machine readableinstructions 700 of FIG. 7 begin with the example encoder 102determining encoding rules for the encoder 102 (Block 702). In someexamples, the example encoder rule manager 302 may determine encodingrules for the encoder by retrieving rules pertaining to encoding ofmedia signals. The example encoder rule manager 302 stores rules (e.g.,parameters, settings, etc.) relating to encoding media signals. In someexamples, the rules may be overall rules associated with audiocharacteristics (e.g., amplitude limits, frequency limitations, etc.)that must be adhered to when encoding a media signal.

At block 704, the example encoder 102 determines characteristics of amedia identification watermark. In some examples, the example mediaidentification watermark manager 306 may store and/or access rulespertaining to the generation of media identification watermarks. In someexamples, these rules may be similar to the rules stored and/or accessedby the example encoder rule manager 302. In some examples, the examplemedia identification watermark manager 306 may access rules from a mediaprovider, service provider, and/or any other entity that is involved indecoding the watermarks, and that controls the characteristics of mediaidentification watermarks.

At block 706, the example encoder 102 determines characteristics of alow power watermark. In some examples, the example low power watermarkmanager 304 determines characteristics of a low power watermark. In someexamples, the characteristics may be determined in coordination with theexample encoder rule manager 302 and/or the example media identificationwatermark manager 306. In some examples, the characteristics of the lowpower watermark are determined to ensure the low power watermark hasdistinct audio characteristics relative to the media identificationwatermark and relative to the media content.

At block 708, the example encoder 102 receives media for watermarking.In some examples, the example audio signal receiver 310 receives a mediaaudio signal from a content provider and/or other entity. The examplemedia may be any media (e.g., a radio show, a song, a podcast, etc.) forwhich tracking (e.g., via watermarking) is to be implemented.

At block 710, the example encoder 102 generates a media identificationwatermark based on the encoder rules and media. In some examples, theexample media identification watermark generator 312 generates a mediaidentification watermark for the media received by the example audiosignal receiver 310. In some examples, the example media identificationwatermark generator 312 may generate a media identification watermarkincluding information from the media identification information receivedby the example encoder 102. In some examples, the media identificationwatermark is generated and incorporated into the media signal throughoutthe entire media signal. In some examples, the media identificationwatermark may be generated and incorporated at the beginning of themedia signal, and/or periodically throughout the media signal. Theexample media identification watermark generator 312 communicates withthe example media identification watermark manager 306 to determinecharacteristics with which the media identification watermark mustcomply. An example media identification watermark is illustrated in theillustrated example of FIG. 6.

At block 712, the example encoder 102 generates a low power watermarkbased on encoder rules and characteristics of the media identificationwatermark. In some examples, the example low power watermark generator314 receives information from the example encoder rule manager 302 andthe example media identification watermark manager 306 associated withrules pertaining to audio characteristics that the low power watermarkmust have. In some examples, the example low power watermark isgenerated and incorporated throughout the entire media signal. In someexamples, the low power watermark is generated and incorporated at thebeginning of the media signal, and/or periodically throughout the mediasignal.

At block 714, the example encoder 102 outputs the watermarked media. Insome examples, the example watermarked audio signal outputter 316outputs the watermarked media. The example watermarked audio signaloutputter 316 outputs the watermarked media to a database for storage(e.g., the example watermarked media data store 104 of FIG. 1), and/ormay directly output the watermarked media for transmission to anaudience.

Flowcharts representative of example machine readable instructions forimplementing the example media monitor 116 of FIG. 3 are shown in FIGS.8-9. In this example, the machine readable instructions comprise aprogram for execution by a processor such as a processor 1212 shown inthe example processor platform 1200 discussed below in connection withFIG. 12. The program may be embodied in software stored on anon-transitory computer readable storage medium such as a CD-ROM, afloppy disk, a hard drive, a DVD, a Blu-ray disk, or a memory associatedwith the processor 1212, but the entire program and/or parts thereofcould alternatively be executed by a device other than the processor1212 and/or embodied in firmware or dedicated hardware. Further,although the example program is described with reference to theflowcharts illustrated in FIGS. 8-9, many other methods of implementingthe example media monitor 116 may alternatively be used. For example,the order of execution of the blocks may be changed, and/or some of theblocks described may be changed, eliminated, or combined. Additionallyor alternatively, any or all of the blocks may be implemented by one ormore hardware circuits (e.g., discrete and/or integrated analog and/ordigital circuitry, a Field Programmable Gate Array (FPGA), anApplication Specific Integrated circuit (ASIC), a comparator, anoperational-amplifier (op-amp), a logic circuit, etc.) structured toperform the corresponding operation without executing software orfirmware.

As mentioned above, the example processes of FIGS. 8-9 may beimplemented using coded instructions (e.g., computer and/or machinereadable instructions) stored on a non-transitory computer and/ormachine readable medium such as a hard disk drive, a flash memory, aread-only memory, a CD, a DVD, a cache, a random-access memory and/orany other storage device or storage disk in which information is storedfor any duration (e.g., for extended time periods, permanently, forbrief instances, for temporarily buffering, and/or for caching of theinformation). As used herein, the term non-transitory computer readablemedium is expressly defined to include any type of computer readablestorage device and/or storage disk and to exclude propagating signalsand to exclude transmission media. “Including” and “comprising” (and allforms and tenses thereof) are used herein to be open ended terms. Thus,whenever a claim lists anything following any form of “include” or“comprise” (e.g., comprises, includes, comprising, including, etc.), itis to be understood that additional elements, terms, etc. may be presentwithout falling outside the scope of the corresponding claim. As usedherein, when the phrase “at least” is used as the transition term in apreamble of a claim, it is open ended in the same manner as the term“comprising” and “including” are open ended.

Example machine readable instructions 800 that may be executed toperform signal identification using a low power watermark areillustrated in FIG. 8. With reference to the preceding figures andassociated descriptions, the example machine readable instructions 800of FIG. 8 begin with the example media monitor 116 performinganalog-to-digital conversion on a received media signal (Block 802). Insome examples, the example analog to digital converter 404 may performanalog-to-digital conversion on a received media signal. In someexamples, the received media signal may already be a digital signal. Insuch examples, the media signal may be immediately received by theexample digital signal receiver 408 and added to the example buffer datastore 416.

At block 804, the example media monitor 116 adds the signal to thebuffer data store and transmits the signal to the low power processor.In some examples, the example analog to digital converter 404 may addthe signal to the example buffer data store 416 and transmit the signalto the example digital signal receiver 408. In some examples, the signalis directly transmitted to the example watermark detector 412, with orwithout temporary storage in the example buffer data store 416.

At block 806, the example media monitor 116 determines if a low powerwatermark is present in the signal. In some examples, the examplewatermark detector 412 determines if a low power watermark is present inthe signal. In some examples, the example watermark detector 412utilizes a least means squares algorithm to determine if a low powerwatermark is present. In some examples, any algorithm may be utilized todetermine if a low power watermark is present. Example approaches fordetermining if a low power watermark is present in the signal aredisclosed in further detail in connection with FIG. 9.

At block 808, the example media monitor 116 determines if the signalincludes a low power watermark. In some examples, the example watermarkdetector 412 outputs an indication to the example digital signalprocessor initiator 414 as to whether the signal includes a low powerwatermark. In some examples, the example watermark detector 412 mayoutput an error value, and/or other value representative of a comparisonbetween an extracted low power watermark from the audio signal and areference low power watermark. In some examples, the example watermarkdetector 412 and/or the example digital signal processor initiator 414utilizes the value to determine if the signal includes the low powerwatermark. In response to the signal including a low power watermark,processing transfers to block 810. Conversely, in response to the signalnot including a low power watermark, processing transfers to block 812.

At block 810, the example media monitor 116 provokes processing of thesignal on the digital signal processor. In some examples, the exampledigital signal processor initiator 418 provokes processing of the signalon the example digital signal processor 418. In some examples, provokingprocessing includes changing the power state of the digital signalprocessor (e.g., changing the digital signal processor from an inactivestate to an active state), initiating a media identification technique,ensuring the example digital signal processor 418 is ready to receive amedia signal, and/or any other method of initiating a processingtechnique for media identification watermark extraction on the exampledigital signal processor 418.

At block 812, the example media monitor 116 determines if the digitalsignal processor is currently processing a signal. In some examples, theexample digital signal processor initiator 414 may determine if theexample digital signal processor 418 is currently processing a signal.The example digital signal processor initiator 414 determines if theexample digital signal processor 418 is currently processing a signal toavoid deletion of an audio signal from the example buffer data store 416that is currently being processed by the example digital signalprocessor 418, or is pending processing by the example digital signalprocessor 418. In response to the example digital signal processor 418currently processing a signal, processing transfers to block 814.Conversely, in response to the example digital signal processor 418 notcurrently processing a signal, processing transfers to block 816.

At block 814, the example media monitor 116 transmits the signal in theexample buffer data store 416 to the example digital signal processor418. In some examples, the example digital signal processor initiator414 communicates to the example buffer data store 416 to transmit thesignal for which a low power watermark has been found to the exampledigital signal processor. In some examples, the example buffer datastore 416 may transmit data currently stored in the example buffer datastore 416 to the example digital signal processor 418. In some examples,the example buffer data store 416 continually transmits the audio signalreceived after the initial indication that the signal includes a lowpower watermark, until an indication from the example digital signalprocessor 418 (e.g., indicating that media identification watermarkshave no longer been found, that the digital signal processor has changedto an inactive state, etc.) to cease transmission to the example digitalsignal processor 418. In some examples, the example watermark detector412 may communicate with the example buffer data store 416 to ceasetransmission to the example digital signal processor 418 when the lowpower watermark is no longer detected. In some examples, the examplebuffer manager 410 may communicate with the example digital signalprocessor 418 and the example digital signal processor initiator 414 tocontrol the transmission of signals to the example digital signalprocessor 418.

At block 816, the example media monitor 116 deletes the signal from theexample buffer data store 416. In some examples, the example buffermanager 410 deletes the signal from the example buffer data store 416 inresponse to the example low power watermark not being found in thesignal, in response to the digital signal processor 418 no longerfinding media identification watermarks, in response to a specifiedamount of time since receiving the audio signal, and/or in response toany other condition. In some examples, the example digital signalprocessor 418 and/or the example digital signal processor initiator 414may communicate with the example buffer manager 410 and/or the examplebuffer store 416 to delete audio signals that do not contain watermarks,or have already been processed by the example digital signal processor418.

Example machine readable instructions 900 that may be executed todetermine if a low power watermark is present in the signal using anexample least means squares algorithm are illustrated in FIG. 9. Withreference to the preceding figures and associated descriptions, theexample machine readable instructions 900 of FIG. 8 begin with theexample media monitor 116 inputting the example audio signal to a linearfilter to extract a filtered watermark output (Block 902). In someexamples, the example watermark detector 410 inputs the example audiosignal 502 to the example linear filter 504 to extract an examplefiltered watermark 506. The example linear filter 504 may implementlinear filtering on the example audio signal 502 using multiplecoefficients that are adjusted by the example adaptive algorithm 514 toattempt to extract the low power watermark from the example audio signal502.

At block 904, the example media monitor 116 subtracts the filteredwatermark output from the known reference low power watermark tocalculate an error value. In some examples, the example summing function510 of the example watermark detector 410 subtracts the example filteredwatermark 506 from the example reference low power watermark 508 tocalculate the example error value 512. In some examples, any othermethod of performing a comparison between the example filtered watermark506 and the example reference low power watermark 508 may be utilized.In some examples, any method capable of determining if the examplefiltered watermark 506 represents a low power watermark can be utilized.

At block 906, the example media monitor 116 determines if the errorvalue satisfies a threshold. In some examples, the example digitalsignal processor initiator 414 may determine if the error valuesatisfies a threshold representative of the example filtered watermark506 being similar to the example reference low power watermark 508. Insome examples, the example watermark detector 410 may itself determineif the error value satisfies a threshold representative of the examplefiltered watermark 506 being similar to the example reference low powerwatermark 508, indicating the presence of a low power watermark in thesignal. In response to the error value satisfying a threshold,processing transfers to block 908. Conversely, in response to the errorvalue not satisfying a threshold, processing transfers to block 910.

At block 908, the example media monitor 116 indicates that the signalincludes the low power watermark. In some examples, the examplewatermark detector 410, and/or the example digital signal processorinitiator 414, indicate that the signal includes the low powerwatermark.

At block 910, the example media monitor 116 indicates that the signaldoes not include the low power watermark. In some examples, the examplewatermark detector 410, and/or the example digital signal processorinitiator 414, indicate that the signal does not include the low powerwatermark.

At block 912, the example media monitor 116 inputs the error value intoan adaptive algorithm to update the coefficients of the linear filter.In some examples, the example error value 512 is input to the exampleadaptive algorithm 514. The example adaptive algorithm 514 then updatesthe coefficients of the example linear filter 504 to attempt to minimizethe example error value 512. For example, the example adaptive algorithm514 may adjust the coefficients such that an example audio signal 502including a low power watermark that is input to the example linearfilter 504 subsequently results in a lower example error value 512 basedon the new coefficients. As a result, the example linear filter 504becomes more accurate at extracting and identifying the lower powerwatermark in the example audio signal 502, when the example audio signal502 includes the low power watermark.

FIG. 10 is a schematic representation 1000 of an example implementationof the low power watermark utilized for signal identification. Theexample schematic representation 1000 includes three charts plottedagainst an example time axis 1002.

The example schematic representation 1000 includes an example mediasignal plot 1004 representing the amplitude of the media signal beingpresented. The example media signal plot 1004 is substantially flat(e.g., not changing in height along the vertical axis) when no mediasignal is being presented.

The example schematic representation 1000 further includes an exampledigital signal processor state representation plot 1006. The exampledigital signal processor state representation plot 1006 includes an “ON”value (e.g., representing the digital signal processor being in anactive mode) and an “OFF” value (e.g., representing the digital signalprocessor being in an inactive mode).

The example schematic representation 1000 additionally includes anexample low power processor state representation plot 1008. The examplelow power processor state representation plot 1008 includes an “ON”value (e.g., representing the low power processor being in an activemode) and an “OFF” value (e.g., representing the low power processorbeing in an inactive mode).

The example schematic representation 1000 includes three instances ofmedia signals 1010 a, 1010 b, 1010 c being presented, as shown in theexample media signal plot 1004. Throughout the entire duration of theexample schematic representation 1000, the example low power processorstate representation plot 1008 indicates that the low power processorremains in the “ON” state. The example low power processor staterepresentation plot 1008 also includes sets of arrows 1014 a, 1014 b,1014 c corresponding to recognition events where the low power processordetected the low power watermark. The example sets of arrows 1014 a,1014 b, 1014 c correspond to recognition events that coincide with theexample media signals 1010 a, 1010 b, 1010 c, indicating that theexample media signals 1010 a, 1010 b, 1010 c include the example lowpower watermark. The example sets of arrows 1014 a, 1014 b, 1014 cadditionally coincide with a change in the example digital signalprocessor representation plot 1006 from the “OFF” state to the “ON”state. The example digital signal processor active events 1012 a, 1012b, 1012 c indicate that the digital signal processor is in an activemode and performing processing on the audio signal. In some examples,the detection of the low power watermark, as indicated by the sets ofarrows 1014 a, 1014 b, 1014 c, cause the digital signal processor to gofrom the “OFF” state to the “ON” state.

The example schematic 1000 illustrates the potential power savings ofutilizing the low power watermark media identification technique, as thedigital signal processor state representation plot 1006 indicates thatthe digital signal processor is only in the “ON” state (e.g., an active,processing mode) when the audio signal is present. The addition of thelow power watermark and corresponding low power processor consequentlyresults in lower power consumption by reducing or eliminating powerdrain by the digital signal processor when there is no watermarked mediato be processed.

FIG. 11 is a block diagram of an example processor platform 1100 capableof executing the instructions of FIG. 7 to implement the example encoder102 of FIG. 3. The processor platform 1100 can be, for example, aserver, a personal computer, a mobile device (e.g., a cell phone, asmart phone, a tablet such as an iPad™), a personal digital assistant(PDA), an Internet appliance, a DVD player, a CD player, a digital videorecorder, a Blu-ray player, a gaming console, a personal video recorder,a set top box, or any other type of computing device.

The processor platform 1100 of the illustrated example includes aprocessor 1112. The processor 1112 of the illustrated example ishardware. For example, the processor 1112 can be implemented by one ormore integrated circuits, logic circuits, microprocessors or controllersfrom any desired family or manufacturer. The hardware processor may be asemiconductor based (e.g., silicon based) device. In this example, theprocessor 1112 implements the example encoder rule manager 302, theexample low power watermark manager 304, the example mediaidentification watermark manager 306, the example media signal processor308, the example audio signal receiver 310, the example mediaidentification watermark generator 312, the example low power watermarkgenerator 314, and/or the example watermarked audio signal outputter 316of FIG. 3

The processor 1112 of the illustrated example includes a local memory1113 (e.g., a cache). The processor 1112 of the illustrated example isin communication with a main memory including a volatile memory 1114 anda non-volatile memory 1116 via a bus 1118. The volatile memory 1114 maybe implemented by Synchronous Dynamic Random Access Memory (SDRAM),Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory(RDRAM) and/or any other type of random access memory device. Thenon-volatile memory 1116 may be implemented by flash memory and/or anyother desired type of memory device. Access to the main memory 1114,1116 is controlled by a memory controller.

The processor platform 1100 of the illustrated example also includes aninterface circuit 1120. The interface circuit 1120 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), and/or a peripheral component interconnect(PCI) express interface.

In the illustrated example, one or more input devices 1122 are connectedto the interface circuit 1120. The input device(s) 1122 permit(s) a userto enter data and/or commands into the processor 1112. The inputdevice(s) can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, an isopoint device, and/or avoice recognition system.

One or more output devices 1124 are also connected to the interfacecircuit 1120 of the illustrated example. The output devices 1024 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay, a cathode ray tube display (CRT), a touchscreen, a tactileoutput device, a printer and/or speakers). The interface circuit 1120 ofthe illustrated example, thus, typically includes a graphics drivercard, a graphics driver chip and/or a graphics driver processor.

The interface circuit 1120 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem and/or network interface card to facilitate exchange of data withexternal machines (e.g., computing devices of any kind) via a network1126 (e.g., an Ethernet connection, a digital subscriber line (DSL), atelephone line, coaxial cable, a cellular telephone system, etc.).

The processor platform 1100 of the illustrated example also includes oneor more mass storage devices 1128 for storing software and/or data.Examples of such mass storage devices 1128 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, redundantarray of independent disks (RAID) systems, and DVD drives.

The coded instructions 1132 of FIG. 7 may be stored in the mass storagedevice 1128, in the volatile memory 1114, in the non-volatile memory1116, and/or on a removable non-transitory computer readable storagemedium such as a CD or DVD.

FIG. 12 is a block diagram of an example processor platform 1200 capableof executing the instructions of FIGS. 8-9 to implement the examplemedia monitor 116 of FIG. 4. The processor platform 1200 can be, forexample, a server, a personal computer, a mobile device (e.g., a cellphone, a smart phone, a tablet such as an iPad™), a personal digitalassistant (PDA), an Internet appliance, a DVD player, a CD player, adigital video recorder, a Blu-ray player, a gaming console, a personalvideo recorder, a set top box, or any other type of computing device.

The processor platform 1200 of the illustrated example includes aprocessor 1212. The processor 1212 of the illustrated example ishardware. For example, the processor 1212 can be implemented by one ormore integrated circuits, logic circuits, microprocessors or controllersfrom any desired family or manufacturer. The hardware processor may be asemiconductor based (e.g., silicon based) device. In this example, theprocessor 1212 implements the example decoder 402, the example analog todigital converter 404, the example low power processor 406, the exampledigital signal receiver 408, the example buffer manager 410, the examplewatermark detector 412, the example digital signal processor initiator414, the example buffer data store 416, the example digital signalprocessor 418, and/or the example data store 420 of FIG. 4.

The processor 1212 of the illustrated example includes a local memory1213 (e.g., a cache). The processor 1212 of the illustrated example isin communication with a main memory including a volatile memory 1214 anda non-volatile memory 1216 via a bus 1218. The volatile memory 1214 maybe implemented by Synchronous Dynamic Random Access Memory (SDRAM),Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory(RDRAM) and/or any other type of random access memory device. Thenon-volatile memory 1216 may be implemented by flash memory and/or anyother desired type of memory device. Access to the main memory 1214,1216 is controlled by a memory controller.

The processor platform 1200 of the illustrated example also includes aninterface circuit 1220. The interface circuit 1220 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), and/or a peripheral component interconnect(PCI) express interface.

In the illustrated example, one or more input devices 1222 are connectedto the interface circuit 1220. The input device(s) 1222 permit(s) a userto enter data and/or commands into the processor 1212. The inputdevice(s) can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, an isopoint device, and/or avoice recognition system.

One or more output devices 1224 are also connected to the interfacecircuit 1220 of the illustrated example. The output devices 1024 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay, a cathode ray tube display (CRT), a touchscreen, a tactileoutput device, a printer and/or speakers). The interface circuit 1220 ofthe illustrated example, thus, typically includes a graphics drivercard, a graphics driver chip and/or a graphics driver processor.

The interface circuit 1220 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem and/or network interface card to facilitate exchange of data withexternal machines (e.g., computing devices of any kind) via a network1226 (e.g., an Ethernet connection, a digital subscriber line (DSL), atelephone line, coaxial cable, a cellular telephone system, etc.).

The processor platform 1200 of the illustrated example also includes oneor more mass storage devices 1228 for storing software and/or data.Examples of such mass storage devices 1228 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, redundantarray of independent disks (RAID) systems, and DVD drives.

The coded instructions 1232 of FIGS. 7-8 may be stored in the massstorage device 1228, in the volatile memory 1214, in the non-volatilememory 1216, and/or on a removable non-transitory computer readablestorage medium such as a CD or DVD.

From the foregoing, it will be appreciated that example methods,apparatus and articles of manufacture have been disclosed that enable anefficient media signal identification process using a low powerwatermark in addition to a media identification watermark. The encodingof a low power watermark with distinct audio characteristics relative tothe media identification watermark and the content of the audio signalenables a low power processor utilizing a least means square algorithmto detect the presence of watermarked media and provoke the more powerintensive media identification processing technique performed on adigital signal processor. The utilization of the low power watermarktherefore enables extraction of media identification watermarks withsignificantly less power consumption by reducing processing utilizationof the digital signal processor. Such improvements in power consumptionare inherently beneficial to advancing the wireless capabilities andoverall form factor of portable media monitors, among other devices.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. An apparatus for media identification based onwatermarks, the apparatus comprising: a first processor to: determine,in response to receiving a signal, if a first watermark is present inthe signal using a first processing technique, the first processingtechnique including: compare a filtered watermark signal to a referencewatermark signal corresponding to a universal watermark; output an errorvalue, wherein the error value is a difference between the filteredwatermark signal and the reference watermark signal, the error valueindicative of whether the first watermark is present in the signal; andin response to the error value satisfying a threshold, reduce the errorvalue associated with a frequency by adjusting coefficients in adirection opposite of a corresponding amplitude to the error value atthe frequency; provoke, in response to the first watermark being presentin the signal, a second processing technique on a signal processor; andthe signal processor to: extract a second watermark in the signal usingthe second processing technique.
 2. The apparatus of claim 1, whereinthe first processing technique requires less processing power than thesecond processing technique.
 3. The apparatus of claim 1, wherein thefirst watermark is a universal watermark that has same characteristicsamong multiple signals associated with media presentations.
 4. Theapparatus of claim 3, wherein the universal watermark has a lengthcorresponding to a length of the second watermark, wherein the secondwatermark is a media identification watermark.
 5. The apparatus of claim1, wherein the signal processor is in a low power mode when the firstwatermark is not present.
 6. The apparatus of claim 1, wherein the firstprocessor is further to alter the signal processor from a low powerstate to a high power state in response to determining the firstwatermark to be present.
 7. The apparatus of claim 1, wherein the secondwatermark is an identification watermark pertaining to the mediarepresented by the signal.
 8. The apparatus of claim 1, wherein thefirst processing technique includes a least means square adaptivealgorithm.
 9. The apparatus of claim 8, wherein the first processingtechnique includes filtering the signal using a linear filter, togenerate the filtered watermark signal.
 10. The apparatus of claim 9,wherein the first processing technique includes an adaptive algorithm,the adaptive algorithm to adjust coefficients associated with the linearfilter based on the error value calculated when comparing the filteredwatermark signal to the reference watermark signal.
 11. A non-transitorycomputer readable storage medium comprising instructions which, whenexecuted, cause a machine to at least: determine, in response toreceiving a signal, if a first watermark is present in the signal usinga first processing technique, the first processing technique including:compare a filtered watermark signal to a reference watermark signalcorresponding to a universal watermark; output an error value, whereinthe error value is a difference between the filtered watermark signaland the reference watermark signal, the error value indicative ofwhether the first watermark is present in the signal; and in response tothe error value satisfying a threshold, reduce the error valueassociated with a frequency by adjusting coefficients in a directionopposite of a corresponding amplitude to the error value at thefrequency; provoke, in response to the first watermark being present inthe signal, a second processing technique on a signal processor; andextract a second watermark in the signal using the second processingtechnique.
 12. The non-transitory computer readable storage medium ofclaim 11, wherein the instructions, when executed, further cause themachine to alter the signal processor from a lower power state to a highpower state in response to determining the first watermark to bepresent.
 13. The non-transitory computer readable storage medium ofclaim 11, wherein the first processing technique requires lessprocessing power than the second processing technique.
 14. Thenon-transitory computer readable storage medium of claim 11, wherein thefirst watermark has a length corresponding to a length of the secondwatermark, wherein the first watermark is a universal watermark that hassame characteristics among multiple signals and the second watermark isa media identification watermark.
 15. A method comprising: determining,in response to receiving a signal, if a first watermark is present inthe signal using a first processing technique, the first processingtechnique including: comparing a filtered watermark signal to areference watermark signal corresponding to a universal watermark;outputting an error value, wherein the error value is a differencebetween the filtered watermark signal and the reference watermarksignal, the error value indicative of whether the first watermark ispresent in the signal; and in response to the error value satisfying athreshold, reducing the error value associated with a frequency byadjusting coefficients in a direction opposite of a correspondingamplitude to the error value at the frequency; provoking, in response tothe first watermark being present in the signal, a second processingtechnique; and extracting a second watermark in the signal using thesecond processing technique.
 16. The method of claim 15 furtherincluding altering a signal processor from a low power state to a highpower state in response to determining the first watermark to bepresent.
 17. The method of claim 15, wherein the first processingtechnique consumes less processing resources than the second processingtechnique.
 18. The method of claim 15, wherein the first watermark is auniversal watermark that has same characteristics among multiplesignals.
 19. The method of claim 15, wherein the second watermark is amedia identification watermark.